Attending ex-girlfriend's wedding, arresting the groom's officer on the spot

In the office, some team members were dozing off in their chairs, while others were eating instant noodles to replenish their energy. Zhang Hui looked at everyone, his heart filled with gratitude: "You've all worked hard. Take a rest first; we have a tough battle to fight this morning."

Sunlight streamed through the office window, marking the start of a new day. Zhang Hui knew that as long as he followed Li Shengli's leads, he would eventually find his killer, give the deceased and his family a just explanation, and expose the evil hidden beneath the murky waters.

The next morning at 9 a.m., as soon as the door to the Criminal Investigation Division's conference room closed, the air was filled with the aroma of rustling papers and coffee. On the long conference table, the case files for Li Shengli were stacked according to categories such as "Crime Scene Investigation," "Autopsy Report," "Surrounding Area Investigation," and "Identity Verification." Each document had colorful sticky notes attached to its edges, with keywords such as "size 43 shoe print," "brass watch fragments," and "suburban smoke extraction equipment" standing out prominently. Lu Chuan sat at the head of the table, his eyes bloodshot from staying up all night. He tapped his fingers lightly on the table, his gaze sweeping over Yang Lin, Zhang Kai, Wang Shuai, Zhang Hui, and others present—confirming the victim's identity was only the starting point; clarifying the suspicion of restaurant owner Zhou Ming and finding the specific location of the "suburban smoke extraction equipment" were the keys to breaking through the case.

"Everyone's here. Report in turn according to your assigned roles, starting with Yang Lin. Explain the details of the crime scene investigation thoroughly, especially any clues that could link to the suspect or the murder weapon." Lu Chuan's voice broke the silence. Yang Lin immediately stood up and projected the crime scene diagram onto the screen. The red dot of the laser pointer landed on the key traces as he spoke.

"Five types of core clues were extracted from the drainage ditch site and require further explanation. The first type is footprints and walking trajectory. Within a 50-meter range upstream from the body discovery point, three men's size 43 athletic shoe prints were found. All of them had a grid pattern with red brick fragments embedded in the pattern, which is completely consistent with the composition of bricks from the demolition site. The stride length was 80-81 cm and the stride width was 18 cm, further confirming that the suspect was 175-180 cm tall and weighed 70-75 kg. The shoe prints extended along the upstream ditch path and were covered by garbage at the abandoned drainage outlet. Combined with the trampling marks on the weeds along the ditch, it can be determined that the suspect's route for disposing of the body was 'upstream path → body discovery point → return along the same route'. The suspect did not enter the surrounding residential area and had a strong counter-surveillance awareness."

“The second category is remains and fibers,” Yang Lin switched to the next photo, which showed a wrench fragment, canvas fragment, and brown fibers in a transparent evidence bag. “30 meters upstream from the body, a piece of iron wrench fragment was extracted. The oil stains on the surface were tested and found to be rust-preventive machine oil commonly used for construction iron machinery, which is the same type of machine oil found in the demolition site warehouse; the canvas fragment is made of the same material as the bag that wrapped the body, and the tear marks on the edges match the shape of the branches of the willow tree by the canal, proving that the bag was torn by a branch and left behind; in addition, three new coarse brown fibers were found in the soil next to the canvas fragment. They were tested and found to be the fibers of a cotton work jacket, which is different from the material of the ‘black jacket’ described by Li Shengli’s wife. It is speculated that they were left behind by the suspect’s clothing.”

Yang Lin put away the laser pointer and added, "The third category is cigarette butts and environmental traces. Under a willow tree 10 meters east of the body, two 'Liqun' cigarette butts were found. The teeth marks on the filters were consistent with those of the previously found cigarette butts. The DNA detected inside the cigarette butts was different from the DNA of the skin tissue fragments found under Li Shengli's fingernails, confirming that they came from the same suspect. In the soil next to the cigarette butts, brass powder consistent with that in Li Shengli's tool bag was detected, suggesting that the suspect had stayed there to observe and had come into contact with Li Shengli's repair tools. The fourth category is metal fragments. A brass fragment embedded in the victim's left wrist was found to be completely consistent with the material of the 'brass watch chain' described by Li Shengli's wife. The polishing marks on the edge of the fragment matched the connection structure of the watch chain, proving that the watch chain broke and embedded itself in the skin during the struggle."

"Can we pinpoint the exact source of the wrench fragments? Besides construction workers, could other industries use cotton workwear fibers?" Lu Chuan pressed, his finger lingering on the "demolition site" marker on the survey map, his brow furrowed slightly. Yang Lin shook his head: "Wrenches are general-purpose items, sold in hardware stores throughout the city, so we can't pinpoint their exact source yet; cotton workwear fibers are industrial-grade, and people in construction, auto repair, and logistics industries could all wear them, but considering clues like engine oil and brick fragments, it's more likely that people in the construction industry used them."

Next, Zhang Kai reported the autopsy findings. The autopsy report on the screen clearly displayed the key data: "The deceased, Li Shengli, male, 46 years old, 178 cm tall, 72 kg, time of death determined through four dimensions to be between 0:6 and 3:2 AM six days ago. The first basis is the characteristics of decomposition: the skin all over the body is in a 'washing woman's hand' state, the putrefactive venous network in the chest and abdomen is distributed in a tree-like pattern, and the lividity in the lower right abdomen has spread to the waist. Combined with the average water temperature of 18℃ in the drainage ditch, it is estimated that the decomposition process has lasted for 5-7 days; the second basis is rigor mortis and livor mortis: rigor mortis has completely subsided, the joints are relaxed, and livor mortis has appeared." The first evidence is a dark purplish-red color that doesn't fade when pressed, consistent with deaths occurring more than 72 hours after death. The second evidence is the stomach contents; only a small amount of brownish, pasty material remained in the intestines, with no undigested food, matching Li Shengli's wife's statement that they ate dinner at 7 pm. Combined with the food digestion rate, the time of death was determined to be 7-8 hours after the meal, i.e., 2-3 am. The third evidence is entomological: water fly larvae (second instar) extracted from the seams of the body's clothing, which would take 4-5 days to mature at the current water temperature, cross-validated with the characteristics of decomposition, ultimately pinpointing the time of death to 1-2 am, 6 days prior.

"The connection between the fatal injury and the murder weapon is key. Any new findings?" Lu Chuan's finger hovered over the "Injury Analysis" page of the report. Zhang Kai switched to the injury photos, his tone serious: "The fatal injury is a mechanical asphyxiation injury to the neck—a 0.8 cm wide band-shaped indentation around the neck with irregular edges and minor skin abrasions. The cotton fibers extracted from the abrasion are completely consistent with the 'brown coarse fibers' found by Yang Lin at the scene. It is speculated that the weapon used was the sleeve of the cotton work jacket worn by the suspect, or a separate strip of cotton cloth. There is obvious bleeding in the neck muscles (sternocleidomastoid muscle and infrahyoid muscle group) corresponding to the indentation, a fracture of the greater horn of the hyoid bone, and no mud in the trachea, proving that the death was caused by strangulation before death, ruling out drowning."

He added, "Two other key injuries require close attention: First, a 2×3cm blunt force injury to the right temporal region. The red brick fragments extracted from the wound cavity are completely consistent with the composition of bricks from the demolition site, indicating that the blunt force used by the suspect was a brick from the demolition site, with moderate force, causing Li Shengli to briefly lose consciousness before strangling him." (End of Chapter)